This invention relates to a needle shield for a hypodermic syringe and needle assembly, and in particular to such a shield which can be activated simply by the application of a linear pushing force in a direction away from the point of the needle.
Covering the needle of a hypodermic syringe after it has been used is extremely important since accidental sticking by a contaminated needle is a frequent source of disease transmission. The traditional cover which is placed over a hypodermic needle by its very nature leads to needle stick since it must be moved toward the needle and if the user does not succeed in placing the cover over the needle the fingers holding the cover probably will be stuck. Such a cover also is susceptible of becoming misplaced. Finally, the installation of such a cover requires a concentrated effort making it a common practice to delay installation of the cover until after an emergency situation has abated thereby creating the possibility of accidental needle stick in the interim.
Accordingly, attempts have been made to provide a needle shield which is attached to the syringe before its use and which can be placed in a position around the needle without the necessity of moving the hands toward the needle. However, the prior art devices of this type all have disadvantages which have prevented their widespread acceptance.
One shortcoming of the prior art shields is that they are complex or utilize a complex latching system. Thus, they are expensive to manufacture, are cumbersome to use and are difficult to latch and unlatch. A prior art device which typifies this problem is La Marche, U.S. Pat. No. 1,921,034.
While somewhat less expensive to manufacture, and simpler to use than La Marche, devices such as those shown in Mitchell, U.S. Pat. No. 4,631,057 and Sampson et al., U.S. Pat. No. 4,573,976 have inherent installation problems. First, they either press fit or are glued onto the syringe they are used with and thus must be sized to fit a particular syringe body exactly. Accordingly, a shield must be made for each different syringe on the market. In addition, if it is not oriented correctly when it is installed, the shieldlatching mechanism of Sampson et al., '976, will cover the volumetric indicia located on the syringe.
Sampson et al., U.S. Pat. No. 4,425,120 provides a much simpler device but it again has installation and operational shortcomings. The pins 47, which carry the shield, must either be manufactured as an integral part of the syringe or they must be installed later by adhesive. The former makes installation of the shield on existing syringes impossible, and the latter is labor intensive and prone to breakage. Furthermore, the Samson et al. '120 cover creates the indexing difficulties mentioned above. In addition, the necessity to rotate the device to unlock and again lock it requires concentration of the user which, in an emergency situation, will result in a delay in deploying the shield. Finally, a locking mechanism of this type can easily become dislodged thereby allowing the shield to fall back away from its extended position.
The present invention overcomes the foregoing shortcomings and limitations of the prior art syringe shields by providing a sleeve guide which attaches to the flange of a hypodermic syringe and a shield which travels on the sleeve guide between extended and retracted positions. The sleeve guide has a two-piece fastener which snaps together over the syringe flange. Thus, the device is easily installed without the necessity that the sleeve guide create a press fit with the chamber of the syringe or be glued to it. Since the size and shape of syringe flanges are fairly uniform, and the fastener does not have to fit the flange precisely, only a few sleeve guides are required to accommodate most existing syringes. Furthermore, since syringe flanges are elongate, in order to accommodate the fingers of the users, the sleeve guide can only be installed in a particular rotational position relative to the chamber of the syringe and thus will not inadvertently cover the volumetric indicia on the syringe.
Depending on the size of the syringe, the sleeve guide has one or two fingers which extend along the sides of the syringe. The fingers have center portions which contact the sides of the chamber of the syringe and inner and distal portions which bow out from the chamber. The fingers are made from a flexible material so that the inner and distal portions can be deflected to where they also are substantially flush with the chamber.
The sleeve which fits over the sleeve guide is a cylindrical tube having a diameter which allows it to fit loosely over the center portions of the fingers but not fit over the inner and distal portions without their being deflected. The sleeve has one or two slots, depending on whether the sleeve guide it will be used with has one or two fingers, and the slots extend across substantially all of its longitudinal extent. The ends of the sleeve guide are open and the end facing the syringe has an annular ledge protruding from its periphery. The sleeve is transparent in order to permit reading the volumetric indicia located on the chamber of the syringe.
As the sleeve is inserted onto the sleeve guide, the distal portions of the fingers are deflected until they reach the slots in the sleeve and then they protrude through the slots to provide tracks for the sleeve to travel along without rotating. When the sleeve is fully inserted on the sleeve guide the needle extends out of it and is uncovered. When in this retracted position the inner portions of the fingers are located inwardly of the slots and thus are deflected by the sleeve. Protrusions located on the inner portions of the fingers are positioned where they will project into the slots and contact their bottom edges. Thus, the protrusions prevent the sleeve from inadvertently being moved from its retracted position.
After the syringe and needle assembly has been used, the ledge at the bottom of the sleeve is pushed which causes the sleeve to pass over the protrusions. The sleeve then is slid along the fingers to an extended position where it completely covers the needle. Since the user contacts the sleeve at the end opposite the needle, and the sleeve is being pushed away from the point of the needle, the user's fingers will not be stuck by the needle while performing this operation. In the extended position the distal portions of the fingers are located beneath the portion of the sleeve which extends below the slots and thus are deflected by the sleeve. A pair of prongs is located on each distal portion such that when the sleeve is in its extended position one of the prongs extends into the slot and engages its bottom edge to prevent the shield from being pulled off of the sleeve guide, and the other prong fits behind the shield to prevent it from being slid back to its retracted position. Thus the needle cannot inadvertently be exposed and the assembly can be discarded in normal trash receptacles.
Since it is easy to move the shield to its extended position, and since there is no danger of being stuck by the needle when doing so, the user normally will move the shield to its extended position immediately after the syringe and hypodermic assembly is used.
Accordingly, it is a principal object of the present invention to provide a needle shield for a hypodermic syringe and needle assembly which can be attached easily to existing syringes.
It is a further object of the present invention to provide such a needle shield which is universal and will fit on most pre-existing syringes.
It is a further object of the present invention to provide such a needle shield which attaches to the syringe through a snap-together fastener.
It is a still further object of the present invention to provide such a needle shield where the snap-together fastener is self-aligning so that the needle shield never obscures the volumetric indicia located on the syringe.
It is a yet further object of the present invention to provide such a needle shield wherein movement to an extended position, where it covers the needle, is along a linear path.
It is a further object of the present invention to provide such a needle shield which is moved to its extended position merely by being pushed in a direction away from the point of the needle.
It is a still further object of the present invention to provide such a needle shield which does not interfere with the operation of the syringe.
The foregoing and other objectives, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.